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July 9 (Reuters) - NTP Inc said it filed patent infringement lawsuits against several of the world's top mobile phone companies including Apple Inc, Google Inc, Microsoft and Motorola Inc.

The privately held company, which is also suing HTC Corpand LG Electronics Inc, won a $600 million from a settlement with BlackBerry maker Research In Motion in 2006 after a long legal battle.

NTP filed said it filed the lawsuits on Thursday in the United States District Court for the Eastern District of Virginia and that it had no option since the companies in question were using its patents without a license.

The eight patents it says are being infringed relate to the delivery of email "over wireless communications systems."

Representatives for Motorola, Microsoft, HTC, LG and Google could not immediately be reached for comment.

Mobile email has become essential for wireless companies whose latest smartphones are more like mini computers and include everything from Web surfing to games.

While Apple has gained a strong foothold in this market with its iPhone, Google has been gaining ground as more phone makers depend on its Android mobile operating system for their flagship phones.

HTC, Motorola and LG all make phones based on Android.

In December, the U.S. Patent and Trademark Office validated 67 of NTP's claims in four patents in the RIM litigation and said RIM infringed three claims, NTP said.

NTP also said on Friday that it filed an appeal to the U.S. Court of Appeals for the Federal Circuit to overturn the patent office's remaining rejections of NTP patent claims. (Reporting by Sinead Carew; editing by Derek Caney)